I used a small elco (electrolytic condensator) of 4.7 uF to do the auto power on. The positive pole of the elco is attached to pin #1 and the negative pole to pin #12 of the I/O connector. This briefly shorts those two together, but not continually. That would cause the XU to power down after 10 seconds.

A little addition to the workaround above; it's possible to use elco's in the range of 0.47 to 4.7 uF and a operating voltage of at least 6.3 Volt. Keep in mind: the higher the capacity of the elco, the longer the 'on button' is 'pushed' at start up. Too long will result in a power down, like in a way that is usual on large PC's.

Keeping the capacity low has also the advantage of short power brown outs; the elco needs to be discharged on power down to be effective as a power on boot up aid, so with lower capacity this will take less time. The only thing to pay attention to is to pick the capacity large enough, so the XU will recognize the power on boot up.

I also have trouble to use external power switch.In my case I also need to have power status of odroid to know when cut of power from PSU.

So here is my solution: The pullup resistor can be in uC like in my case or external one.In the below picture I connect it to pin 1 but not sure if this pin is always powered, if not then connect it before main switch of your power.

Also note that PWRON (pin12) should be connected to colector of this NPN.